1. Field of the Invention
The present invention generally relates to digital voice communications in a cellular system and, more particularly, to a method and apparatus for making measurements of bit error rate (BER) at a cellular base station.
2. Description of the Prior Art
Cellular mobile telephone systems are now widely installed in many metropolitan areas throughout the United States. The service area covered by a cellular system is divided into a number of cells, each having a base station which can effect a telephone connection to any mobile unit located in the cell. The base stations are all connected to and controlled by a central mobile telephone switching office (MTSO) that connects to the telephone network. For additional background on cellular mobile telephone systems, the reader is referred to the textbook by William C. Y. Lee entitled Mobile Cellular Telecommunications Systems, McGraw-Hill (1989).
In order to assure quality service, it is necessary to test the equipment which comprise the various subsystems of the cellular system. The base stations pose a particular problem since these are typically unmanned stations which function automatically under the control of the MTSO. Normally, various pieces of expensive test equipment are needed to perform bit error rate (BER) tests on cellular base station transceivers. The performance of the tests is labor intensive, requiring highly skilled technicians to perform them. To provide complete testing of the base stations in the cellular system, it is necessary for technicians to go to each base station, set up the test equipment, run the tests, and record the results. As a result, there may be long periods between tests at any given base station during which time the quality of service could be deteriorating. Since it is important for developing the market to provide high quality service at the least cost, it is desirable to provide apparatus and a method for permitting frequent and automatic tests at base stations.